Author:
Sklute Elizabeth C.,Leopo Deborah A.,Neat Kaylee A.,Livi Kenneth J. T.,Dyar M. Darby,Holden James F.
Abstract
Some thermophilic bacteria from deep-sea hydrothermal vents grow by dissimilatory iron reduction, but our understanding of their biogenic mineral transformations is nascent. Mineral transformations catalyzed by the thermophilic iron-reducing bacterium Desulfovulcanus ferrireducens during growth at 55°C were examined using synthetic nanophase ferrihydrite, akaganeite, and lepidocrocite separately as terminal electron acceptors. Spectral analyses using visible-near infrared (VNIR), Fourier-transform infrared attenuated total reflectance (FTIR-ATR), and Mössbauer spectroscopies were complemented with x-ray diffraction (XRD) and transmission electron microscopy (TEM) using selected area electron diffraction (SAED) and energy dispersive X-ray (EDX) analyses. The most extensive biogenic mineral transformation occurred with ferrihydrite, which produced a magnetic, visibly dark mineral with spectral features matching cation-deficient magnetite. Desulfovulcanus ferrireducens also grew on akaganeite and lepidocrocite and produced non-magnetic, visibly dark minerals that were poorly soluble in the oxalate solution. Bioreduced mineral products from akaganeite and lepidocrocite reduction were almost entirely absorbed in the VNIR spectroscopy in contrast to both parent minerals and the abiotic controls. However, FTIR-ATR and Mössbauer spectra and XRD analyses of both biogenic minerals were almost identical to the parent and control minerals. The TEM of these biogenic minerals showed the presence of poorly crystalline iron nanospheres (50–200 nm in diameter) of unknown mineralogy that were likely coating the larger parent minerals and were absent from the controls. The study demonstrated that thermophilic bacteria transform different types of Fe(III) (oxyhydr)oxide minerals for growth with varying mineral products. These mineral products are likely formed through dissolution-reprecipitation reactions but are not easily predictable through chemical equilibrium reactions alone.
Subject
Microbiology (medical),Microbiology
Reference57 articles.
1. Reductive dissolution of Fe(III) (hydr)oxides by cysteine: kinetics and mechanism;Amirbahman;J. Colloid. Interface. Sci.,1997
2. Carbonate and sulphate green rust: mechanisms of oxidation and reduction;Antony;Electrochim. Acta,2008
3. ATR-FTIR spectroscopic investigation on phosphate adsorption mechanisms at the ferrihydrite-water interface;Arai;J. Colloid. Interface. Sci.,2001
4. “Potential pathways to maghemite in Mars soils: the key role of phosphate,”;Barron;Lunar and Planetary Science Conference XXXV, The Highlands, Texas, Abstract,2004
5. Hydromaghemite, an intermediate in the hydrothermal transformation of 2-line ferrihydrite into hematite;Barron;Am. Mineral.,2003